Method and tooling for forming sheet material with bend controlling displacements

ABSTRACT

A method of preparing a sheet of material for bending along a bend line includes the step of forming at least one displacement in the thickness direction of the sheet of material, the displacement including a flat zone substantially parallel to the sheet of material with a portion of the periphery of the flat zone extending along and adjacent to the bend line, and including an angled transition zone interconnecting the flat zone with a remainder of the sheet of material. The forming step is preferably accomplished using one of a stamping process, a punching process, a roll-forming process and an embossing process. A sheet of material suitable for bending using the process also is disclosed, as are the use of coatings, shin guards and displacing the area of the sheet between bending inducing slits.

RELATED APPLICATIONS

This application is a Continuation-in-Part of U.S. patent Ser. No.11/080,288 filed Mar. 14, 2005 and entitled SHEET MATERIAL WITH BENDCONTROLLING DISPLACEMENTS AND METHOD FOR FORMING THE SAME, which isContinuation-in-Part of U.S. patent application Ser. No. 10/795,077filed Mar. 3, 2004 and entitled SHEET MATERIAL WITH BEND CONTROLLINGDISPLACEMENTS AND METHOD FOR FORMING THE SAME, which is aContinuation-in-Part of U.S. patent application Ser. No. 10/672,766filed Sep. 26, 2003 and entitled TECHNIQUES FOR DESIGNING ANDMANUFACTURING PRECISION—FOLDED, HIGH STRENGTH, FATIGUE-RESISTANTSTRUCTURES AND SHEET THEREFOR, which is a Continuation-in-Part of U.S.patent application Ser. No. 10/256,870 filed Sep. 26, 2002 and entitledMETHOD FOR PRECISION BENDING OF SHEET MATERIALS, SLIT SHEET ANDFABRICATION PROCESS, which is a Continuation-in-Part of U.S. patentapplication Ser. No. 09/640,267 filed Aug. 17, 2000 and entitled METHODFOR PRECISION BENDING OF A SHEET OF MATERIAL AND SLIT SHEET THEREFOR andnow U.S. Pat. No. 6,481,259 B1, the entire contents of whichapplications is incorporated herein by this reference.

This application also claims U.S. Patent Provisional Application No.60/682,057 filed Mar. 17, 2005 and entitled METHOD AND TOOLING FORFORMING SHEET MATERIAL WITH BEND CONTROLLING DISPLACEMENTS, the entirecontents of which application is incorporated herein by this reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates, in general, to the precision folding ofsheet material and, more particularly, relates to preparing the sheetmaterial for bending using punching, stamping, roll-forming, embossingand similar processes, and then bending or folding the sheet intothree-dimensional structures.

2. Description of Related Art

The present method and apparatus are based upon slitting and groovinggeometries disclosed in depth in the above set forth relatedapplications, which are each incorporated herein by reference in theirentireties. In these related applications several techniques ormanufacturing processes for forming slits and grooves that willprecisely control bending of a wide variety of sheet material aredisclosed, including laser cutting, water jet cutting, stamping,punching, molding, casting, stereo lithography, roll forming, machining,chemical-milling, photo-etching and the like. Some of these processesfor fabricating bend-inducing slit geometries can be more expensive thanothers. For example, laser cutting will inherently involve additionalcost as compared to, for example, punching or stamping, but punching andstamping may not be particularly well suited to sheet material ofrelatively heavy gauge.

The precision bending slit geometries of the above-identified relatedapplications may be advantageously applied to numerous structures whichare formed from relatively thin gauge sheet material. These structurestend to be more driven by the need for complex and precise bendingpatterns than they are by strength or fatigue resistance requirements.An example of one type of structure which can be formed of a relativelythin gauged sheet material, and yet requires precision and complexbending, is electronic component chassis, such as, computers, audioreceivers, television sets, DVD players, etc.

As is noted in prior related U.S. patent application Ser. No.10/672,766, flat sheets, which are slit or grooved in accordance withthe teachings of that prior related application, can have electricalcomponents mounted to the flat sheets using “pick-and-place” techniques.The sheets may then be folded into enclosures or housings in which allof the components are spatially related in the desired positions insidethe housing. The “pick-and-place” techniques greatly reduce cost, asdoes the ability to fold a flat sheet into a precisely dimensionedenclosure using relatively low-force bending techniques. While suchelectronic chassis can be formed using laser cutting or water jetcutting, there is considerable advantage if lower cost slit-forming orgroove-forming techniques can be employed. Thus, lower cost fabricationprocesses such as punching, stamping, roll-forming or the like, will behighly advantageous to use with relatively thin gauge material if theydo not lose the precision advantages that the slits geometries of therelated applications can produce.

Moreover, slit-forming techniques, such as punching, stamping androll-forming, can produce slits which have essentially zero kerf or slitwidth dimension, while laser and water jet cutting remove material andproduct slits having a measurable kerf or width dimension. Sheets havingzero kerf slits have the advantage of being more closed along the bendline after the sheets are bent. Thus, they do not tend to open up asmuch during bending as sheets having measurable kerf dimensions. Thismakes the zero kerf sheets amenable to coating with a protective layerthat will seal and close the bend line to allow them to be used inapplications in which electromagnetic shielding, corrosion resistance,attractive appearance, or fluid tightness is required.

Accordingly, it is an object of the present invention to provide amethod for preparing sheet material for precision bending along a bendline, which method is relatively low in cost and adaptable to a widerange of applications employing sheet material.

A further object of the present invention is to provide a low costmethod for preparing sheet material for bending, which method is capableof precise bending free of cumulative bending errors, is suitable forcomplex bending patterns, and requires only minimal force to effectbending.

Another object of the present invention is to provide a sheet ofmaterial for bending in which slits or grooves are formed using low-costmanufacturing processes that are capable of producing structures whichcan be sealed, are fluid-tight, corrosion resistant or must have anattractive appearance.

The bendable sheet material and bend-inducing sheet forming method ofthe present invention have other objects and features of advantage whichwill be set forth in more detail hereinafter in the following Best Modeof Carrying Out the Invention, as exemplified and illustrated by theaccompanying drawing.

DISCLOSURE OF THE INVENTION

The method of preparing a sheet of material for bending along a bendline of the present invention is comprised, briefly, of the step offorming at least one displacement in the thickness direction of thesheet of material with the portion of the periphery of the displacementclosest to the bend line providing an edge and an opposed faceconfigured and positioned to produce edge-to-face engagement of thesheet of material during bending. The displacement is preferably formedusing one of a punching, stamping, roll-forming, embossing, chemicalmilling or etching process in which dies, machine tools, a knife orchemical agent form a slit or shear line of zero kerf or a groove in thesheet material. When dies are employed, the periphery of thedisplacement caused by the die, which is closest to the bend line issheared at least partially, and often completely, through the thicknessdimension of the sheet of material proximate the bend line. Mostpreferably, a plurality of displacements are formed along the bend line,with alternate displacements being positioned on opposite sides of thebend line. In the most preferred form the periphery which is closest tothe bend line is, in fact, superimposed on the bend line so that the jogdistance between displacements on opposite side of the bend line isessentially zero. The displacements, however, can have a jog distance inthe range of about −1 to about +1 times the thickness dimension of thesheet. The displacements also may be plastically deformed by die sets toproduce the opposing edge and face structures. Upon bending, the sheetof material may not fracture or rupture along the plastically deformeddisplacements, so that the bend will be maintained as a fluid-tightcontinuous structure along the bend line, or it may rupture to provide aface and opposed edge similar to sheared sheets. While it is preferredto displace the tongues which are defined inside the slits or grooves,it also is possible to displace the areas longitudinally between theslits or groove and still achieve edge-to-face precision bends.Moreover, the bending direction is preferably in the direction ofdisplacement of the tongues, but if lower precision can be toleratedbending can be in the opposite direction.

A sheet of material suitable for bending along a bend line is alsoprovided which comprises, briefly, a sheet having at least onedisplacement in the thickness direction of the sheet, with a portion ofthe displacement closest to the bend line providing an edge and anopposing face configured to produce edge-to-face engagement of the sheetof material on opposed sides of the portion of the periphery duringbending. Most preferably a plurality of displacements are positionedalong the bend line on alternating sides of the bend line. A continuouslayer of coating material can be placed on the sheet before bending tofurther insure that resulting bend will be fluid-tight, corrosionresistant and attractive. The displacements in the sheet of material canextend partially through the sheet or completely through it, and thesheet can be bent in the direction of the displacements for maximumprecision or in an opposed direction by relying on the oblique bendingstraps to control the precision. Optionally, but less desirably, thesheet may be bent in the opposite direction when the precisionachievable by edge-to-face bending is not required.

One aspect of the present invention is directed to a method of preparinga sheet of material for bending along a bend line comprising the step offorming at least one displacement in the thickness direction of thesheet of material, the displacement including a flat zone substantiallyparallel to the sheet of material with a portion of the periphery of theflat zone extending along and adjacent to the bend line. Thedisplacement also includes an angled transition zone interconnecting theflat zone with a remainder of the sheet of material. The forming steppreferably provides the portion of the periphery adjacent the bend linewith an edge and the sheet of material with a corresponding opposed faceconfigured and positioned to produce edge-to-face engagement of thesheet of material during bending. The forming step may shear the sheetof material entirely through the thickness dimension along the portionof the periphery. The forming step may be accomplished using one of astamping process, a punching process, a roll forming process, a shearingknife-based and an embossing process.

In one embodiment, a plurality of displacements may be formed in thesheet of material along the bend line with each displacement having aflat zone having a periphery portion proximate the bend line to providea plurality of edges and opposed faces for edge-to-face bending of thesheet of material. Each flat zone may have the periphery portionsubstantially superimposed on the bend line. The forming step may beaccomplished using one of a stamping process, a punching process, a rollforming process, a shearing knife-based and an embossing process. Theforming step may be accomplished using a turret press to form each ofthe plurality of displacements, wherein the turret press is relocatedwith respect to the sheet of material to the desired location of each ofthe plurality of displacements. The forming step may be accomplishedusing a modular die set including a number of die units corresponding innumber to the number of displacements. The plurality of displacementsmay be differently sized, wherein the die units are similarlydifferently sized and complementary in number and size to the pluralityof displacements.

In one embodiment, the periphery portion of displacements may bepositioned on opposite side of the bend line at a jog distance from eachother less than the thickness dimension of the sheet of material. Thejog distance may be in the range of about −0.5 to about +0.5′ times thethickness dimension of the sheet of material. The peripheral portions ofdisplacements may be positioned on opposite sides of the bend line todefine bending straps oriented to extend obliquely across the bend line.The bending straps may have a strap width that is approximately 2-5times the thickness of the material.

A layer of coating material may be adhered to the sheet of materialacross the portion of the periphery of the displacement. The adheringstep may form a continuous layer of flexible coating material.

Preferably, the flat zone is elongated and includes curved ends. Theperiphery of the curved ends may be semicircular in shape.

The method may further include the step of bending the sheet of materialalong the bend line. The bending step may be accomplished manually.

Another aspect of the present invention in directed to a sheet ofmaterial suitable for bending along a bend line, wherein the sheet maybe formed by any one of the above methods. Preferably, the sheet ofmaterial has at least one displacement in a thickness direction of thesheet of material, the displacement including a flat zone substantiallyparallel to the sheet of material with a portion of the periphery of thedisplacement extending along and adjacent to the bend line, andincluding an angled transition zone interconnecting the flat zone with aremainder of the sheet of material.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1A is a fragmentary, top plan view of a sheet of material havingbend controlling displacements formed therein in accordance with thepresent invention.

FIG. 1B is an enlarged, fragmentary, end elevation view, in crosssection of the sheet of FIG. 1A, taken substantially through the planeof line 1B-1B in FIG. 1A.

FIG. 1C is a cross sectional view corresponding to FIG. 1B with thesheet having been bent by 90 degrees from the flat condition of FIG. 1B.

FIG. 1D is a cross sectional view corresponding to FIG. 1B of analternative embodiment of the sheet in which a protective coatingadhered to the sheet of material.

FIG. 1E is a cross sectional view corresponding to FIG. 1C of the bentcoated sheet of FIG. 1D.

FIG. 2A is a fragmentary, top plan, schematic view of a sheet ofmaterial corresponding to FIG. 1A with only a single displacement orsheared tongue being shown for ease of understanding.

FIGS. 2B and 2C are views corresponding to FIGS. 1B and 1C of the sheetshown in FIG. 2A.

FIG. 3A is a fragmentary, top plan, schematic view of a sheet ofmaterial corresponding to FIG. 1A with only a single displacement orsheared tongue being shown, which tongue has been sheared and displacedbeyond the sheet thickness dimension.

FIGS. 3B and 3C are views corresponding to FIGS. 1B and 1C of the sheetof FIG. 3A.

FIG. 4A is a fragmentary, top plan, schematic view of a sheet ofmaterial corresponding to FIG. 1A having an alternative embodiment of asingle tongue having a reinforced central tongue deformation.

FIGS. 4B and 4C are views corresponding to FIGS. 1B and 1C of the sheetof FIG. 4A.

FIG. 4D is a cross section view taken substantially along the plane ofline 4D-4D in FIG. 4.

FIG. 5A is a fragmentary, top plan, schematic view of a sheet ofmaterial corresponding to FIG. 1A having an alternative embodiment of asingle tongue which has been plastically deformed and displaced in thethickness direction of the sheet.

FIGS. 5B and 5C are views corresponding to FIGS. 1B and 1C of the sheetof FIG. 5A.

FIG. 5D is a view corresponding to FIG. 5C in which the sheet hasfractured or ruptured during bending.

FIG. 6A is a fragmentary, top plan schematic view of a sheet of materialcorresponding to FIG. 1A in which an alternative embodiment to adisplacement having a continuous periphery is shown partially shearedthrough the thickness dimension of the sheet.

FIGS. 6B and 6C are views corresponding to FIGS. 1B and 1C of theembodiment of the sheet of FIG. 6A.

FIG. 7A is a fragmentary, top plan, schematic view of a sheet ofmaterial corresponding to FIG. 6A in which the displacement in the sheethas been sheared only partially through one side of the periphery andcompletely through an opposite side of the periphery.

FIGS. 7B and 7C are views corresponding to FIGS. 1B and 1C of the sheetof FIG. 7A.

FIG. 8 is a front elevation view of a bent sheet of material havingdisplacements of the type shown in FIGS. 2A-2C with a bend-covering shinguard, shown in broken lines, and illustrating upstanding securementtabs.

FIG. 9 is an end elevation view of the sheet of material of FIG. 8 withthe shin guard shown in solid lines mounted to the securement tabs.

FIG. 10 is a front elevation view of an alternative embodiment of bentsheet of material with a shin guard shown in broken lines and anattachment structure.

FIG. 11 is an end elevation view of the sheet of material of FIG. 10with the shin guard shown in solid lines mounted to the sheet by theattachment structure.

FIG. 12A is a side elevation schematic view of a sheet of materialformed in accordance with the present invention and positioned on afixed tool plate for bending by a rotary cylinder and movable linkage.

FIG. 12B is a side elevation schematic view of the sheet of material ofFIG. 12A after partial bending of the sheet on the tool plate.

FIG. 12C is a side elevation schematic view of the sheet of material ofFIG. 12A after a 90 degree bend.

FIG. 13A is a side elevation schematic view of a sheet of materialformed in accordance with the present invention and positioned on afixed tool plate for bending by a pneumatic bending bladder.

FIG. 13B is a side elevation schematic view of the sheet of material ofFIG. 13A after a 90 degree bend.

FIG. 14A is a top plan, schematic view of a sheet of material that hasbeen grooved in accordance with the present invention.

FIG. 14B is an end view of the sheet of FIG. 14A.

FIG. 14C is a side elevation view of the sheet of FIG. 14A with the halfof the sheet above the bend line shown bent outwardly of the page.

FIG. 14D is an end view of the sheet as bent in FIG. 14C.

FIG. 15A is a top plan schematic view of a sheet of material that hasbeen grooved and provided with stress relieving features in accordancewith an alternative embodiment of the present invention.

FIG. 15B is an end view of the sheet of FIG. 15A.

FIG. 15C is a side elevation view of the sheet of FIG. 15A with the halfof the sheet above the bend line shown bent outwardly of the page.

FIG. 15D is an end view of the bent sheet of FIG. 15C.

FIG. 16A is a top plan schematic view of a sheet of material havingshear lines controlling bending and having the areas betweenlongitudinal adjacent shear lines on the same side of the bend linedisplaced to produce edge-to-face bending.

FIG. 16B is an end view of the bent sheet of FIG. 16A.

FIG. 16C is a side elevation view of the sheet of FIG. 16A with theupper half of the sheet shown bent into the page.

FIG. 16D is an end view of the bent sheet of FIG. 16C.

FIG. 16E is an enlarged, cross sectional view of the sheet of FIG. 16A,taken substantially along the plane of line 16E-16E in FIG. 16A.

FIG. 16F is a cross sectional view of the sheet of FIG. 16E as bent byninety degrees.

FIG. 17 is a fragmentary, schematic top plan views similar to FIG. 1 ofanother sheet of material having bend controlling displacements formedtherein.

FIG. 18A and FIG. 18B are enlarged, fragmentary, end elevation views, incross-section of the sheet of FIG. 17, taken substantially along line18-18 in FIG. 17, FIG. 18B illustrating further, optional working of thesheet of FIG. 17.

FIG. 19 is an enlarged, fragmentary, end elevation view, incross-section of the sheet of FIG. 18A subsequent to folding.

FIGS. 20A, 20B and 20C are schematic views of tooling which may be usedto form bend controlling displacements in the sheet of FIG. 17 inaccordance with the present invention.

FIG. 21A and FIG. 21B are schematic top plan views of other tooling thatmay be used to form the bend controlling displacements in the sheet ofFIG. 17.

FIG. 22A and FIG. 22C are fragmentary, schematic top plan views similarto FIG. 17 of another sheet of material having bend controllingdisplacements formed therein.

FIG. 23A and FIG. 23B are schematic top plan views of tooling that maybe used to form the bend controlling displacements in the sheet of FIG.22A and FIG. 22B, respectively.

FIG. 24 is a schematic top plan view of tooling similar to that shown inFIG. 23A and FIG. 23B.

FIG. 25A, FIG. 25B, and FIG. 25C are schematic views of tooling whichmay be used to form relatively short bend controlling displacements inaccordance with the present invention.

FIG. 26 is a schematic end view of other tooling that may be used toform the bend controlling displacements in sheets similar to that shownin FIG. 17.

FIG. 27 is a cross-sectional view of a sheet, similar to that shown inFIG. 17, said sheet including bend controlling displacements formed bythe tooling of FIG. 26.

FIG. 28 is a exploded schematic view of the tooling of FIG. 26.

FIG. 29 is an exploded perspective view of the tooling of FIG. 26.

FIG. 30 is a partial, exploded perspective view of the tooling of FIG.26, showing punch blades inserted into a punch blade block.

FIG. 31 is a partial perspective view of the tooling of FIG. 26, showingthe

FIG. 32A, FIG. 32B, and FIG. 32C are schematic views of exemplary sizesof such blades of FIG. 30.

FIG. 33 is an exploded perspective view of a other tooling similar tothat shown in FIG. 29.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with thepreferred embodiments, it will be understood that they are not intendedto limit the invention to those embodiments. On the contrary, theinvention is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of theinvention, as defined by the appended claims.

The present method and apparatus for precision bending of sheet materialis based upon the slitting geometries disclosed in the above-identifiedprior related applications, which are incorporated herein by referencein their entireties.

As noted in connection with the prior related applications, processesfor forming the slits which will control and precisely locate thebending of sheet material include such processes as punching, stamping,roll-forming, machining, photo-etching, chemical machining,oxy-acetylene and the like. These processes are particularly well suitedfor lighter weight or thinner gauge material, although they also can beemployed for sheet material of relatively heavy gauge. The thicker orheavier gauged materials often are more advantageously slit or groovedusing laser cutting or water jet cutting equipment.

As described in the prior related applications, one highly advantageousapplication for the precision bending of sheet material is in connectionwith electronic component chassis. Such chassis often are highly complexso as to enable the positioning of a multiplicity of components inthree-dimensional arrays inside the eventual housing for the electronicequipment. Since laser cutting and water jet cutting are both somewhatmore expensive, it is particularly desirable to be able to form chassisfor electronic equipment, and numerous other lower cost housings and thelike, using-low cost, high-production techniques such as punching,stamping, roll forming and the like. The present application, therefore,illustrates how these lower cost fabrication processes can be applied torelatively thinner gauged sheet material with great advantage.

Turning now to FIGS. 1A-1C, a sheet of material generally designated 21,is shown in FIG. 1A having a plurality of slits 22 positioned proximateand along a bend line 23. The slits can be seen to have ends which curveaway from bend line 23, and the curved slit ends define therebetweenbending straps 24 that have center lines that extend obliquely acrossbend line 23, in a manner described in substantial detail in priorrelated application Ser. No. 10/672,766. As will be seen, longitudinallyadjacent slits 22 are positioned alternatively on opposite sides of bendline 23 along the length of the bend line, which is the preferredarrangement, but is not absolutely required.

As also may be seen in FIG. 1A, slits 22 are positioned in a laterallydisplaced positions from bend line 23, but this has been done primarilyto illustrate the position of the bend line. In the most preferred formof the invention, when light gauge materials are being prepared forbending, slits 22 will be substantially superimposed on bend line 23.This is preferred because it facilitates the use of the same die setsfor a wider range of sheet material thicknesses.

As described in prior related U.S. patent application Ser. No.10/672,766, the “jog” distance between slits 22 is defined as thelateral distance between the slits on opposite sides of the bend line.In the most preferred form of the embodiments in the presentapplication, therefore, the jog distance is substantially equal to zero,that is, the slits are positioned precisely on bend line 23 so thatthere is no lateral spacing between slits on the opposite sides of thebend line, except at the curved ends. As indicated in the prior relatedapplications, the jog distance between slits relative to bend line 23 ispreferably less than the thickness dimension of sheet 21. Obviously, ajog distance of zero meets that requirement.

Additionally, as can be seen for slits 22 a and 22 b at the right handend of sheet 21, a negative jog distance also can be employed. As willbe seen, slit 22 a extends across bend line 23, as does slit 22 b. Thisis acceptable within the teaching of the present invention and willproduce the edge-to-face bending along bend line 23 that is desired forprecise, controlled bending. For the thinner gauged materials typicallyemployed in electronic equipment chasses, the jog distance between slits22 is preferably in the range of about −0.5 to about +0.5 times thethickness dimension, t, (FIG. 1B) of sheet 21. As the jog distancebetween slits becomes increasingly negative over about −0.5 times thethickness of the sheet of material, there is a tendency for the sheet tobend along two bend lines, which bends are positioned at the edges ofthe slits, rather than a single bend line positioned between the edgesof the slits. At about 0.8 times the thickness of the sheet, forexample, the two bend line phenomena has been seen to occur in 0.060sheet metal.

When a negative jog distance is employed with slits 22 having a zerokerf dimension, the slit will remain relatively closed along its lengtheven after a 90 degree bend. If the slit is formed with a kerf, forexample, by laser cutting, and a negative jog distance is employed,there is a tendency for the material on opposite sides of the slit toseparate or “daylight” upon bending, for example, to 90 degrees. This,however, can be entirely acceptable, depending upon the application.

As will be described in considerable detail below, the most preferredapproach to punching or stamping slits into sheet 21 is to displace atongue or enclosed area of attached slug in the thickness direction ofthe sheet by dies which shear the sheet. It will be understood fromprior related applications, however, that slits 22 also can be formed asshear lines or slits in which there is no displacement of the sheet, forexample, by using a knife, rather than a die that also displaces aportion of the sheet. One of the advantages of forming a displacement inthe sheet, rather than slitting it with a knife, is that edge-to-facesliding of material on opposite sides of slits 22 is reduced or notrequired. The displacement of the sheet also reduces the bending forcesrequired by insuring that each edge and face will move in the rightdirection during bending.

In the preferred form, slits 22 are formed by displacement in athickness direction so that a portion of the periphery of thedisplacement closest to bend line 23 provides an edge 26 and an opposedface 27 configured and positioned to produce edge-to-face engagement ofthe sheet of material on opposite sides of the periphery during bending.As shown in FIG. 1B, a D-shaped tongue 28 has been downwardly displacedto provide a face 27 against which a lower corner 26 or edge on theopposite side of slit 22 from tongue 28 will engage when sheet 21 isbent. As illustrated best in FIGS. 1B and 1C, a portion of the slitperiphery is superimposed on the plane of bend line 23. The next slit,which is into the page in FIG. 1B, has a similar D-shaped tongue 28 awhich has been downwardly displaced to provide a face 27 a against whichan edge 26 a will engage.

When sheet 21 is bent, for example, by 90 degrees, edges 26, 26 a pivotaround and engage faces 27,27 a at about a midpoint in the faces. Asbending continues, they act as opposed fulcrums which are positioned onbend line 23 (that can be seen in FIG. 1C to have rotated by 45degrees). Thus, almost immediately as the bend begins, the edges 26,26 aare rotated into engagement with faces 27,27 a, with result that bendingis very precisely controlled to occur about bend line 23. The obliquelyoriented bending straps 24 pull and maintain edges 26,26 a against faces27,27 a during bending to maintain the fulcrums in contact with theopposed faces. This edge-to-face engagement is described in even moredetail in the prior related applications.

The illustrations in FIGS. 1A and 1B are greatly enlarged in thicknessto enable the edge-to-face contact to be more clearly illustrated. Itwill be understood, however, that sheet 21 can be relatively thin, forexample, 0.060 inches, with tongues 28 downwardly displaced in thethickness dimension by only 0.030 inches. These dimensions, however,obviously are not critical other than to indicate that in thin sheetmaterial the displacements of the tongue material are not very large.

As will be seen from FIG. 1C, edges 26,26 a tend to be held by straps 24into tight engagement with faces 27,27 a. Thus even at the slits 22 thesheet material on both sides of the periphery of the slits closest tothe bend line will be in contact with each other over the length of theslits. This tends to allow the bent sheet to be used in applications,for example, where electromagnetic shielding is required or even inapplications where fluids need to be contained. It is preferred,however, in order to further insure a fluid-tight bend that acontinuous, preferably flexible, coating material be adhered or bondedto the sheet across the area of slits 22. This embodiment of the presentinvention can be seen in FIGS. 1D and 1E, which correspond to FIGS. 1Band 1C. A continuous layer of a flexible sealant or coating 29 can beseen to have been deposited, adhered or bonded to downwardly facingsurfaces of sheet 21 across the slits. This is most preferablyaccomplished while sheet 21 is in a substantially flat, but sheared,condition, as shown in FIG. 1D. Upon bending to the position of FIG. 1E,the coating 29 will tend to be crushed or compressed between faces 27and 27 a and the underneath side of the sheet of material. Mostprotective coatings, such as epoxies and paints, will be sufficientlyflexible and compressible to accommodate the compression and bending ofthe sheet without fracturing. Thus, coating 29 will insure that there isa continuous surface that is be fluid-tight. Obviously, it would also bepossible within the scope of the present invention to simply spray acoating on the bent sheet of FIG. 1E, but for many applications applyingcoating 29 to the flat, but punched, stamped or roll-formed sheet ismore preferred since the bend lines 23 can be at complex interiorlocations that would be hard to coat after bending.

In cases where full coverage of both sides of the street with a flexiblesealing coating is desired, one generally applies (prior to bending) aflexible coating 29 to both sides of the sheet in the embodiment of bentD-shaped tongues 28 as shown in FIGS. 2A-2C. As can be clearly seen, thebent tongue 36 rotates with respect to the sheet about edge 38. Thisleaves the coating intact and continuous on the top or upwardly facingsurface of the sheet, while the coating on the under or downwardlyfacing surface is compressed under tab end (37) as noted in FIGS. 1D and1E.

As will be apparent to one skilled in the art, the displacement ortongues 28 of FIGS. 1A-1D can be readily formed by punching, stamping,embossing and roll-forming processes. A set of dies can be used to punchdown tongues 28 with a portion of the periphery forming thebend-controlling slit 22 in the opposed edges and faces. As shown in thedrawing, the phantom line 31 is not a clearly defined shoulder, but isthe point at which tongue 28 reaches the top surface of the sheet andhas not been downwardly displaced. FIGS. 1A-1C show a tongue ordisplacement 28 which has essentially been half sheared by the punchingdies so that the upper surface of the displacements 28 have beendisplaced downwardly to about one-half the thickness dimension of thesheet, which causes the dies on the lower half of the edge to shear awayand complete faces 27 and 27 a.

In FIGS. 2A-2C, the process is the same, only the punching orroll-forming device have sheared displacements or tongues 36 downwardlyby the full thickness, t, of the sheet. Thus a face 37 on the peripheryof displacement or tongue 36 is now displaced until the upper edge offace 37 is positioned at edge 38 on the opposite side of slit 22. Thistends to produce a point-to-point contact at edge 38 with the corner offace 37 during bending, as shown in FIG. 2C. Nevertheless, the edgefulcrum 38 on the edge of face 38 again precisely controls the locationof bending, together with the opposed tensioning of oblique bendingstraps 24 along bend line 23.

In FIGS. 3A-3C, sheet 21 has been sheared during punching so that a face42 of displacement or tongue 41 is now down below lower surface 43 ofthe sheet of material. Edge 44, therefore, is not engaged with oppositeface 42 and will not engage face 42 during bending, as best can be seenin FIG. 3C. Instead, control of the position of the bend relative tobend line 23 is accomplished by opposite, obliquely-extending, bendingstraps 24. Use of bending straps 24 to control the positioning of thebend of the sheet of material is less precise than can be achievedthrough edge-to-face engagement of opposite sides of the slit peripheryduring bending. Nevertheless, oblique bending straps 24 can producereasonably precise bends that require low bending forces and the bendingstraps do not excessively twist or stress during bending. Accordingly,for applications where there is more tolerance as to the dimensionalrequirements of the resultant product, over-displacement of tongues 41to the FIG. 3B position can be employed. It should be noted that sets ofdies can be used to progressively shear displacement or tongue 41 to theposition of 3B and then displace tongue 41 upwardly at a second diestation to the position of FIG. 2B or 1B. If, for example, it is desiredor necessary to be certain that the downwardly displaced tongue has beensheared completely through and yet is repositioned so that the edge willengage the opposed face upon bending, a two-station operation will beperformed.

In the embodiment of FIGS. 4A-4D, a fully sheared displacement or tongue51 is shown which corresponds to the full shear of the tongue of FIGS.2A-2C. Tongue 51, however, is formed in FIGS. 4A-4D with a downwardlydeformed central reinforcing portion 52. This provides for engagementbetween lower edge 26 with face 27 at a corner or point located on bendline 23. Even further downwardly displaced central portion 52 of tongue51 insures that over bending the sheet will be limited.

Turning now to FIGS. 5A-5D, a displacement of the sheet material toprovide an edge and opposed face by plastic deformation, rather thanshearing, is shown. Sheet 21 has been downwardly displaced at 61typically by stamping or roll-forming dies that are not provided withsharp edges so that the downward displacement has resulted in a plasticdeformation of area 62 of the sheet. Upon bending, the bending strips 24will again be tensioned or bent and thereby pull the sheet on oppositesides of the bend line 23 together so that area 62 deforms withoutshearing or fracturing. In effect, a virtual face on the end ofdisplacement 61 engages a virtual edge 63 on bend line 23 so as toprecisely control the location of the bend. This approach is best suitedto ductile sheet material and it has the advantage of resulting in afluid-tight bend.

In FIG. 5D an alternative is shown in which fracturing or rupturingoccurs at face 64 so that the virtual face becomes an actual face 64. Interms of precision bending, it does not matter whether or not fracture64 occurs and edge 63 is bending off of an actual face 64 or a virtualface at the end of downward displacement of tongue 61.

In FIGS. 6A-6C and 7A-7C, the displacements have a closed periphery orare formed as slugs of material that are downwardly displaced onalternative sides of bend line 23. It will be understood that for easeof illustration a plurality of these slug-type displacements have notbeen shown, but they would be positioned as shown in FIG. 1A, preferablywith the peripheral side closest to the bend line positioned insuperimposed relation to bend line 23. Such oval-shaped displacements orslugs are readily amenable to punching, stamping, roll-forming andsimilar high production, low-cost fabrication processes. The slug maytake various shapes including ‘D’ shape and non-uniform shapes thatproduce diagonal straps and edge-to-face engagement.

In FIG. 6A, sheet 22 has been formed with an oval-shaped displacement 71having a portion of its periphery 22 closest to bend line 23 downwardlydisplaced as shown in FIGS. 6B and 6C. The downward displacement orshearing of displacement 71 produces a face 27 against which lower edge26 across periphery 22 bears. As the sheet is bent, face 27 pivots aboutface 26 to the position shown in FIG. 6C and oblique straps 24 betweenthe ends of longitudinally adjacent oval displacements 71 are bent asdescribed above for straps 24 between tongues 28. Since this a halfshear of displacement 71, the result is essentially the same as thatachieved in FIGS. 1A-1C except there is a remote side 72 of theperiphery of displacement 71 that also is sheared. As can be seen fromFIG. 6B, remote side 72 is in the oval bore punched into the sheet so asto support face 27 during pivoting of edge 26 for precise location ofbend on bend line 23.

FIGS. 7A-7C are similar to FIGS. 6A-6C only the portion of periphery ofthe oval displacement or slug 81 on bend line 23, namely, the bendcontrolling slit 22, has been sheared by the full thickness of thesheet, while remote peripheral side 82 has only been half sheared. Edge26, therefore, pivots on the upper corner of face 27 in a manner similarto that shown in FIGS. 2A-2C.

Although not shown, oval displacements or slugs 71 and 81 also can becompletely punched or stamped out of sheet 21 to leave oval holes alongthe sheet. Such holes will define obliquely extending bending straps 24skewed in opposite directions at opposite ends of each of the holes.These bending straps extend across the bending line 23 and will againproduce bending along bending line 23, but without edge-to-faceengagement because the slug faces 27 are now gone. While providing lessprecision, such an embodiment will produce reasonably accurate bendingalong bending line 23.

In FIGS. 8-11, two alternative embodiments of the punched or stampedsheets of the present invention are shown in which “shin guards” havebeen added to the corners of the bent sheets. In prior related U.S.patent application Ser. No. 10/672,766, the use of corner coverings overthe bend lines so as to present a smooth corner surface was described.Such coverings are referred to herein and in prior related applicationsas “shin guards,” and FIGS. 8-11 illustrate two embodiments of themanner in which shin guards can be secured to the corners of bentsheets.

In FIG. 8, a sheet of material 21 has been bent at a right angle. Sheet21 has a plurality of tongue displacements 28 constructed as shown inconnection with FIGS. 2A-2C. The upper corner of faces 27 of suchdisplacements are in edge-to-face engagement with the edge 26 on theother side of the periphery of tongue displacement 28. Punched intosheet 21 are a plurality of outwardly extending securement tabs 91 whichare used to couple shin guard 92 around the corner of the bent structureand across bend line 23. In the embodiment shown in FIGS. 8 and 9, shinguard 92 includes a cavity 94 dimensioned to receive tab 91, and thecavity preferably has a tapered entrance surface 96 which leads to anoutwardly facing shoulder 97 that engages with inwardly facing shoulder98 on the tabs 91. The shin guard, therefore, can simply be positionedover the tabs 91 and then urged toward the bent sheet 21 to causeshoulders 97 to snap in behind inwardly facing surfaces 98 of the tabsand thereby secure the shin guard to the corner of the bent structure.Alternatively, the shin guard may be slid in place along the corner.

In FIGS. 10 and 11, openings 101 are periodically provided in sheetmaterial 21 and a shin guard 103 is provided having tapered and neckedprotrusions 104. Protrusions 104 are urged through openings 101 so thatan outwardly facing inwardly shoulder 106 snaps in behind inwardlyfacing surface 107 of the bent sheet 21. Again, the displacements ortongues 28 are constructed as shown in connection with FIGS. 2A-2C.

One of the important features of the slit or displacement geometriesdescribed in this application, and the prior related applications, isthat folding of the sheet of material requires relatively small forces.Bending straps 24 preferably comprise less than a majority of thematerial along the bend line and they are twisted and bent duringbending of the sheet material. The fulcrum between edge 26 and face 27and the long lever arm of the sheet on both sides of the bend line,makes bending of the sheet with relatively low force very simple. It ispossible, for example, to place an edge of the sheet in a slot or grooveand then manually apply a force to the opposite edge to easily bend thesheet. In most cases where the sheet material would be bent for anelectronic chassis, the sheet can be bent by hand. It is most preferred,however, to be able to perform the bending in an automaticmachine-implemented process, for example, in a progressive die assemblyin which the sheet is prepared for bending at a first station by formingdisplacements along the bend line, and the sheet is thereafter moved toanother station and then bent by relatively low-force bending apparatus.

FIGS. 12A-C show a mechanical bending apparatus in which a fixed toolplate 110 supports a sheet 21, which has been prepared for bending inthe manner described above. A bending cylinder 111 is mounted to amovable linkage or arm 112 for downward displacement, as shown by arrow113. As cylinder 111 is brought down against sheet 21, an edge 114 of anotch 116 in the cylinder engages sheet 21 and begins to rotate thecylinder and linkage 112 in a clockwise direction. As the linkage 112continues to move downwardly, cylinder 111 continues to rotate to theposition 21 so as to form shown in FIG. 12C. Alternatively, the toolplate 110 can be movable or both tool plate 110 and cylinder 111 can bemovable.

An alternative approach shown in FIGS. 13A and 13B is for tool plate 110to have a pneumatic bladder 121 positioned over edge 122 of the toolplate. As bladder 121 is inflated to the condition shown in FIG. 13B, itengages the unsupported portion of sheet 21 and drives it down to thebent position shown in FIG. 13B. The low bending force required toeffect the bend of FIG. 13B will easily permit the use of pneumaticbending systems.

Other bending equipment suitable for use for bending the sheets of thepresent invention would include press brakes, robotic devices and othersuitable means.

In FIGS. 14A-14D and 15A-15D, the use of machining, chemical milling orphoto etching of grooves into the sheet using geometries of the priorrelated applications is described. In FIG. 14A, a sheet 221 is formedwith a plurality of grooves 222 along a bend line 223 as above taught inconnection with displacements or shear lines 22. In the preferred form,an edge 226 of grooves 222 falls on or is substantially superimposedrelative to the plane of bend line 223. Grooves 222 alternate onopposite sides of bend line 223 and between longitudinally adjacentgrooves 222 are bending straps 224, which will be seen to extendobliquely across bend line 223.

In FIG. 14C, sheet 221 has been bent out of the page in FIG. 14C ortoward grooves 222. The result will not be edge-to-face engagement ofactual fulcrums to produce precise bending, but instead the bending willbe caused by the equal tension on oblique bending straps 224, which willproduce bending substantially along bend line 223. The precision ofbending toward the grooves will not be quite as good as can be achievedwith edge-to-face bending, but the precision is quite acceptable formany applications, for example, in connection with chemically etchedfolded plane structures and/or electronic chassis components.

In this regard, it should be noted that the embodiments of the presentinvention shown in FIGS. 1A-7C are all shown as having been bent in thedirection of the displacement of the tongues or slugs formed in thesheet during preparation of the sheet for bending. Those sameembodiments, however, could also be bent in an upward direction, thatis, against the direction of displacement of the tongues or slugs duringslitting of the sheets. Such reverse bending will cause the bendingstraps 24 to control the precision of the bend, rather than edge-to-faceengagement, but the straps will give a reasonably precise bend along thebend line 23.

Sheet 221 of FIGS. 15A-15D has been prepared for bending by grooving,with the grooves having stress relieving lands or areas 228 at each end.Again, the grooves 222 a do not go through the complete thickness of thesheet and they define bending straps 224 a that are oblique to bendingline 223 a. Again, the sheet has been bent into the grooves, rather thanaway from them, and straps 224 a are used to control the position of thebend along bend line 223 a.

Turning now to FIGS. 16A-16F, an embodiment of the present invention isshown in which the material between longitudinally adjacent arcuateslits on the same side of the bend line is displaced, rather than thetongues or slugs defined by the slits. In FIG. 16A a sheet of material321 is shown having a plurality of slits 322 positioned on alternatingsides of bend line 323. Obliquely extending bending straps 324 areprovided, and slits 322 define tongues 328 and intermediate areas 330 oneach side of the arcuate slit 322.

Unlike the embodiments previously described, however, D-shaped tongues328 are not displaced but remain in the plane of sheet 321. Instead, thematerial or area 330 longitudinally adjacent to or between tongues 328on the same side of bend line 323 is upwardly displaced, as best may beseen in FIG. 16E. Thus, during the punching, roll-forming, embossing,stamping or the like, the shear which produces slits 322 and faces 327is an upward shear in which area 330 is upwardly displaced from theplane of sheet 321. The lower corner or edge 326 of upwardly displacedarea 330 bears on the corner of face 327. As the sheet is bent to theposition of FIG. 16F, edge 326 will slide down face 327 and bend bendingstrap 324 precisely about rotated bend line or plane 323. The resultantbent sheet is also shown in FIGS. 16C and D, although they are rotatedby 90 degrees relative to FIG. 16F.

As was above described in connection with the other embodiments, theembodiment of FIGS. 16A-16F employs a displacement process in which thesheared slits 322 have geometries according to the prior relatedapplications. Preparation of sheets for low-force precise bending can beaccomplished using low-cost fabrication techniques such as punching,stamping, roll-forming and the like.

In one embodiment shown in FIG. 17, displacements 420 are formed in asheet of material 421 in a manner similar to the slits, tongues, anddisplacements discussed above. In this embodiment, the displacementsinclude a modified tongue 428 which includes a flat zone 431 and atransition zone 432. The flat zone is substantially parallel to theoverall plane of sheet 421, while the transition zone extends at anangle and interconnects the flat zone with the remainder of the sheet,as most clearly seen in FIG. 18A.

In the preferred form, displacements 420 are formed by displacement inthe direction of the thickness of material so that a portion of theperiphery of the displacement closest to bend line 423 provides an edge426. The displacement process also forms a corresponding opposed face427 configured and positioned to produce edge-to-face engagement of withthe edge during bending. As shown in FIG. 17, displacement 420 includesan elongated tongue 428 having substantially semicircular ends. In theillustrated embodiment, the ends of tongue 428 are substantiallysemicircular, however, one will appreciate that the actual geometry ofthe ends may vary. For example, curves having multiple radii may beused, and oval, elliptical, parabolic and/or other suitable curvedshapes may also be used.

As shown in FIG. 18A, elongated tongue has been downwardly displaced toprovide a face 427 against which a lower corner or edge 426 of tongue428 will engage when sheet 421 is bent along bend line 423. Asillustrated best in FIG. 17 and FIG. 18A, a portion of the slitperiphery is superimposed on the plane of bend line 423. One willappreciate, however, that the portion of the slit periphery may belocated a suitable jog distance from the bend line, as is discussedbelow.

The next slit, which is into the page in FIG. 18A, has a similarelongated tongue 428 a which has been downwardly displaced to provide aface 427 a against which an edge 426 a will engage.

Preferably, the tongue is displaced downwardly a distance that isapproximately 60-100% of the thickness of the sheet, and most preferablyapproximately 80% the thickness of the sheet. Such configuration willprovide a point of engagement between edge 426, 426 a and face 427, 427a, respectively, that is below the midpoint of the face, and preferably,positioned at a point that is approximately 60-110% of the sheetmaterial thickness away from the outside surface of sheet 421 (e.g.,approximately 60-110% of the sheet material thickness away from the topsurface of sheet 421 as shown in FIG. 18A), more preferably 60-100%, andmost preferably, approximately 80% of the sheet material thickness awayfrom the outside surface of sheet 421. One will appreciate that theoutside surface of the sheet refers to the surface of sheet 421 that isadjacent the bend line forming the external corner as opposed to thesurface forming the internal corner.

When sheet 421 is bent, for example, by 90 degrees, edges 426, 426 apivot around and engage faces 427, 427 a below midpoint in the faces.One will appreciate, however, that the point of engagement may be at orbelow the midpoint of the face, preferably at a point that is spacedapproximately 60-100%, preferably 60-100% away from the outside surfaceof the sheet, and more preferably at about 80% from the outside surface.As bending continues, the point of engagement of each displacement actas opposed fulcrums which are positioned on bend line 423. Thus, almostimmediately as the bend begins, the edges 426, 426 a are rotated intoengagement with faces 427, 427 a, with result that bending is veryprecisely controlled to occur about bend line 423. The bending straps424 pull and maintain edges 426, 426 a against faces 427, 427 a duringbending to maintain the fulcrums in contact with the opposed faces.

One will also appreciate that the elongated tongues may be furtherworked to modify their final position with respect to the sheet. Forexample, the elongated tongues may be “flatten backed” in which case thetongues are, following displacement, hit with a flat punch tool to pushthe tongues partially or fully back into the cavity created duringdisplacement, as shown in FIG. 18B. Flatten back can either be local tohave flanges sit flush over one or more faces, or along the entire bendline allowing the sheet material to fold back upon itself to create ahemmed sheet edge or boarder.

As was the case above, the illustrations in FIGS. 18 and 19 are greatlyenlarged in thickness to enable the edge-to-face contact to be moreclearly illustrated. It will be understood, however, that sheet 421 canbe relatively thin, for example, 0.060 inches, in which case tongues 428may be downwardly displaced in the thickness dimension preferably in therange of approximately 0.030 to 0.070 inches.

As will be seen from FIG. 19, edges 426, 426 a tend to be held by straps424 into tight engagement with faces 427, 427 a. Thus even at thedisplacements 420 the sheet material on both sides of the periphery ofthe slits closest to the bend line will be in contact with each otherover the length of the displacements. Such contact promotes foldsymmetry as the engagement of edges 426,426 a with faces 427, 427 a issubstantially uniform along the length of the bend line.

The configuration of elongated displacements accommodates a wider rangeof strap widths W and jog distances, that is, the distance between slitsas discussed above. For example, the configuration of elongateddisplacements may be used with strap widths that are approximately 2-5times the thickness t of the sheet, and with approximately 10% to 10%jog and produce a very consistent fold quantity. Such configurationallows greater latitude in geometries used in populating a bend linewith displacements thereby more readily accommodating for various lengthsheets and more readily accommodating for “obstacles” which may lay onor adjacent the bend line. For example, if the sheet of material has arecess or an aperture located along the bend line, the spacing betweenadjacent displacements and/or the jog distance of the displacements maybe more readily varied to accommodate for such obstacles. One willappreciate that certain applications, jogs greater than 10% will alsoproduce adequate fold accuracy. The configuration of elongateddisplacements also reduces the amount of strap twisting about the axisof the strap and promotes bending of the strap about the bend line. Asstrap twist is reduced, the strap width is less critical whereby strapsof varying width may be used along the same fold line, as will bediscussed in greater detail with respect to FIG. 24 below.

In promoting pure bending and minimizing strap twist, the configurationof the elongated displacements may facilitate lower bending forcesrequired to initiate and complete folding along the bend line. Asengagement of edges 426, 426 a with faces 427, 427 a commences upon theonset of folding, and because strap twist is limited, the overall amountof plastic deformation and material strains generated during the foldingprocess may be reduced thereby reducing bending forces. For example, thefolding of sheet 421 illustrated in FIGS. 18 and 19 generates lessmaterial strain and plastic deformation due to the minimal strap twistthat occurs.

Furthermore, the elongated-displacement configuration of sheet 421, andthe reduced plastic deformation and material strain generated duringbending, promotes coating adhesion. As noted above, a flexible sealantor coating (see, e.g., FIGS. 1D and 1E) can be applied to the sheetwhile the sheet is in a substantially flat, but sheared, condition, asshown in FIG. 18A. Upon bending to the position of FIG. 19, the amountof crush or compression the coating undergoes during bending will bereduced commensurate to the reduction of plastic deformation andmaterial strain and thus will adhere better during folding. Thus, sheet421 may be painted in the flat state (see, e.g., FIG. 18A) and folded(see, e.g., FIG. 19) without loosing paint quality. Furthermore, as nonew surfaces are generated during folding, that is, no surfaces thatwere not already exposed prior to bending, there are not unpaintedsurfaces that will appear once the material is folded.

Elongated displacements 420 can be readily formed by punching, stamping,embossing, roll-forming processes, and the like. The configuration ofelongated displacements 420 are also well suited for fabrication bymeans of turret punching, as schematically shown in FIGS. 20A-20C, aswell as by other soft-tooling means. One will appreciate that suchsoft-tooling means are conducive to low-volume production (e.g.,prototyping) medium volume production (as opposed to high-volumeproduction using hard-tooling means). As shown in FIG. 20B, a turretpunch assembly 440 includes a die body 441 having a recess 442, a diepunch 443, and a die ejector 444 which may be configured to move as aunit in a conventional manner. In particular, the turret punch assemblymay be positioned with respect to sheet 421 such that die body 441 ispositioned beneath, and die punch 443 is positioned above, sheet 421 atthe desired position of elongated displacement 420. Once die body 441 ispositioned against the bottom surface of sheet 421, die punch 443impacts against the top surface of sheet 421 causing the tongue todisplace downwardly into recess 442. One will appreciate that the diebody need not necessarily include a recess. The die body can have apositive form in which case the displacements can be punched up.

The configuration and dimensions of die punch 443 generally conform tothe desired shape of flat zone 431, while the configuration anddimensions of die body 441 and recess 442 generally conform with thedesired shape of the transition zone 432. The tight tolerance betweenthe right side of die punch 443 and die body 441 cause tongue 428 toshear along bend line 423, while the increased tolerance between theleft side of die punch 443 allows for non-shearing displacement oftransition zone 432. Optionally, a die ejector 444 may be used to ejecttongue 428 from die body 442. One will appreciate that a die ejector mayonly be necessary in certain cases, for example, in the case of thinnersheet materials, by may be utilized with thicker materials as well. Onewill further appreciate that other well known means such as strippingmay also be used in which the sheet material is extracted from thepositive form of the punch. In both cases, such ejection can be form upor form down in both soft-tooling and hard-tooling applications.

Once elongated displacement 420 is formed, turret punch assembly 440 maybe repositioned with respect to sheet 421 and the process repeated toform elongated displacement 421 a, and/or subsequent elongateddisplacements. Alternatively, sheet 421 may be repositioned relative tothe turret punch assembly, as necessary, to form the various elongateddisplacements.

One will appreciate that the position of the turret punch assembly withrespect to the sheet may be controlled by conventional means. Forexample, computer numeric control (CNC) may be used to control thelocation of one or more turret punch assemblies. In particular a singleturret punch assembly can form a first elongated displacement (e.g.,420), be repositioned with respect to sheet 421, and rotated 180°, andform a second elongated displacement (e.g., 420 a), and so on.

In another embodiment shown in FIG. 21A, a die set 450 having apredetermined configuration of elongate-displacement-forming surfacesmay be provided which stamps or punches a number of elongateddisplacements (e.g., 420, 420 a, etc.) simultaneously. Die set 450 mayinclude a die body 451 having a plurality of recesses 452 thatcorrespond with complementary set of die punches 453 which move inunison in order to form several elongated-displacements simultaneously.

FIG. 21B illustrates another die set similar to that shown in FIG. 21A,except that die set is formed of a plurality of modular die units 460,each unit corresponding in size and shape to a desired elongateddisplacement. One, two, three or more die units may be used to form acorresponding number of elongated displacements. The modular units maybe interconnected to one another by any suitable means. In some aspects,the modular units resemble conventional typesetting that a plurality ofdie units may be configured to form any desired number of elongateddisplacements 420, 420 a, etc.

Turning now to FIGS. 22A and 22B, the configuration of elongateddisplacements required for a particular sheet of material may varydepending upon the geometry and configuration of the sheet of material.As one will appreciate, there are certain advantages in “standardizing”the size of elongated displacements in order to reduce tooling costs andotherwise simplify the design process. For example, theelongated-displacements may be standardized in one, two, three or more“standard” sizes for sheet materials of a particular thickness,particular type of material and/or other parameters.

As shown in FIG. 22A, elongated displacements 520, 520 a of a firstlength (e.g., having a length of approximately 1.4 inches) are used incombination with elongated displacements 530 of a second shorter length(e.g., approximately 0.7 inches). The use of different-length elongateddisplacements allows a designer to ensure that the strap widths fallwithin a preferred range (e.g., approximately 2-5 times the thickness tof sheet 520).

In the embodiment of FIG. 22A, there is no terminal stamp ordisplacement, that is, no displacement extending to the edge of sheet521. Such a no-terminal-stamp configuration is advantageous in that oneneed not worry about providing clearances to stamp neighboring sheetsand the need for a short smile configuration for terminal straps.

As noted above, the configuration of the elongated displacements of thepresent invention allows a wider range of strap lengths to be used. Inthis embodiment, the number and size of elongated displacements has beenselected such that the strap widths between elongated displacements 530,520, 520 a and 530 a all remain within the preferred range ofapproximately 2-5 times the thickness of the material. In contrast,sheet 621 of FIG. 22B includes terminal stamps or displacements 630 and630 which extend to the terminal edge of the sheet. Again, however, thesize and number of elongated displacements have been selected such thatthe strap widths between elongated displacements 630, 620, 620 a and 630a remain within the preferred range of strap widths.

In order to form the elongated displacements of different lengths, diesets of corresponding lengths may be provided. For example, in the caseof the modular die sets, long die units 460 may be used in combinationwith medium die units 461, as shown in FIG. 23A, to form the elongateddisplacement configuration of sheet 521 shown in FIG. 22A. Similarly,long die units 460 may be used in combination with short die units 462,as shown in FIG. 23B, to form the configuration of sheet 621 shown inFIG. 22B.

Further still, one will appreciate that various combinations of long,medium and short die unites may be used in order to provide a widervariety of elongated displacement configurations. For example and asshown in FIG. 24, long die units 460 are used in combination with mediumand short die units 461, 462. In this embodiment, shims 465, 466 ofvarying widths are also used in order to provide further adjustment ofstrap widths along the bend line. As noted above, the range of strapwidths may vary within the preferred range of approximately 2-5 timesthe thickness of the material. The strap widths may even be as much asapproximately 6 or 7 times the thickness of the material, and possiblymore, which in some instances is desirable in that the straps performdifferently by rolling instead of twisting. In particular, the portionsof the straps immediately adjacent the elongated displacements willstill tend to pull and maintain edges against faces in the manner thatis discussed above (see, e.g., edges 26,26 a and faces 27,27 a in FIG.1C). As such, the immediately adjacent portions be under increasedtension and exhibit some twisting. In contrast, the remaining middleportion of the straps will not be under such increased tension and willhave an increased tendency to roll about the bend line. Strap roll asthe sheet material is bent about the bend line may require less energyas opposed to strap twist and thereby may work the metal less during thebending process. Also, with thicker straps, there is a higher percentageof material connecting the two planes of the bent sheet that extendsacross the bend line.

One will further appreciate that the standardized sizing of theelongated displacements may also be used in conjunction with turretpunch press assemblies. For example, turret punch press assembly 470,having a die body 471 and a die punch 473 as shown in FIGS. 25A-C isdimensioned and configured to form short elongated displacements. Onewill further appreciate that the standardized sizing will also benefitboth turret punching and hard tool stamping as well as ease thetransition from prototyping (e.g., with turret punching) to production(e.g., with hard tool stamping). One will appreciate that otherhard-tooling methods may also be employed to form the bendingcontrolling displacements in sheet material in accordance with thepresent invention. As shown in FIG. 26, elongated displacements 720 canbe readily formed in sheet 721 by punching, progressive dies, and otherhard-tooling means. Such hard-tooling means are conducive to high-volumeproduction of product quickly and cost effectively.

As shown schematically in FIG. 26, a hard-tooling assembly 740 generallyincludes a die block 752 having a plurality of recesses 755, a pluralityof punch blades 772 which are received in recesses 769 of a punch bladeblock 762. The recesses of die block 752 and the punch blades 772 aredimensioned and configured to form elongated displacements 720 in sheet721.

Preferably die block 752 and punch blade block 762 are mounted torespective upper and lower punch units 757, 764, which are keyed to oneanother in slides such that they reciprocate toward and away from oneanother in an otherwise conventional manner. In the illustratedembodiment, the die block is mounted to the upper punch unit while thepunch blade block is mounted to the lower punch unit. One willappreciated that the assembly could be reversed with the die blockmounted on the lower unit and the punch blade block mounted on theupper. In order to facilitate service, maintenance, and adjustability,the die block and punch blade block are removably mounted to the upperand lower units by upper and lower mounts 760, 767, respectively. Therespective blocks may be fastened to the mounts and/or upper and lowerunits by suitable means including, but not limited to, threadedfasteners, dowels and other suitable means.

In one embodiment, the die block and the punch blade block may be formedby electron discharge machining (EDM) and/or other suitable means.

Optionally, the hard-tooling assembly 750 includes a stripper plate 779that may be used to eject tongues 728 from punch blades 772. One willappreciate that a stripper plate may only be necessary in certain cases,for example, in the case of thinner sheet materials. The stripper platemay be provided with a stripper plate insert 781 having apertures 786which are dimensioned and configured to have close tolerances withrespect to the punch blades 772. Preferably, the stripper plate insertis removably mounted on the stripper plate by suitable means including,but not limited to threaded fasteners. One will appreciate that removalof the stripper plate insert provides one with access to the punchblades and/or punch blade block for service and maintenance.

The configuration and dimensions of die punch 443 generally conform tothe desired shape of flat zone 431, while the configuration anddimensions of die body 441 and recess 442 generally conform with thedesired shape of the transition zone 432. The tight tolerance betweenthe right side of die punch 443 and die body 441 cause tongue 428 toshear along bend line 423, while the increased tolerance between theleft side of die punch 443 allows for non-shearing displacement oftransition zone 432.

Turning now to FIG. 29, FIG. 30, and FIG. 31, the hard tooling assemblyis shown in exploded, and partially exploded, perspective views whichillustrate the orientation the components with respect to one another,and which also show that a plurality of punch blades may be provided toproduce a line of bend-controlling displacements simultaneously. Onewill appreciate that the number and dimension of punch blades may varydepending upon the particular design criteria of the product beingformed.

As shown in FIG. 29, the punch blades may be provided with détentes 774which may be used in conjunction with otherwise conventional biasedlocking means provided within punch blade block 762 to releasably engagethe punch blades within the recesses 769 of the punch blade block 762.One will appreciate that other suitable locking means may be used.

Turning now to FIG. 30, punch blades 772 are inserted into the punchblade block 762 such that the blades extend a minimal amount upwardlyfrom the block. Such configuration provide the punch blades with morelateral stability and thus minimizes the bending moment of the punchblades and thereby serves to promote longer wear and tear. One willappreciate that utilizing a relatively thin stripper plate insert 781allows the punch blades 772 to extend a minimal amount from the punchblade block 762 and still be effective in producing the elongateddisplacements 720 of sheet 721.

FIG. 31 is a further perspective view showing the orientation of theprimary components of the hard-tooling assembly in the assembled stateas shown in cross-section in FIG. 26. One will appreciate that inoperation, upper punch assembly 757 will descend toward lower punchassembly 764 such that die block 752 will move sheet 721 downwardlyagainst stripper plate insert 781, and in turn, move sheet 721 andstripper plate insert 781 toward the lower punch assembly 764. In doingso, punch blades 772 will effectively extend through stripper plate 781and into recesses 755 of die block 752 to form the bending controllingdisplacements 720 in sheet 721. As the upper punch unit retractsupwardly and away from the lower punch unit, stripper plate 779 isbiased upwardly by a nitrogen cylinder and/or other suitable means tostrip sheet 721 away from the punch blades.

In the illustrated embodiment, the punch blades have a flat surface,that is, one that is substantially parallel to the sheet of material.Such a flat configuration is advantageous in that it will lessen wear onthe punch blades and lengthen the life span of the punch blades. Forexample, the punch blades having flat bottoms would prohibit and/orprevent shearing that may occur with sloped bottom punches. Furthermore,sloped bottom tools generally have more wear, are more expensive to makeand difficult to reshape.

Turning now to FIG. 32A, FIG. 32B, and FIG. 32C, the punch blades may beprovided in a variety of sizes and dimensions. Preferably, thecross-sectional profile of the punch blades are provided in standardizedsizes which may be particularly suited for particular sheet materialshaving particular thicknesses, materials, rigidity and other parameters.For example, punch blades having a 2 mm width may be provided forforming bend controlling displacements in relatively thinner materials,a 3 mm width for relatively medium-thickness materials, and a 4 mm widthfor relatively thicker materials. As shown in the figures, the punchblades may have varying lengths in a manner similar that that asdescribed above in FIG. 22 through FIG. 24.

One will appreciate that hard-tooling assemblies may be provided in avariety of configurations. For example, the assembly shown in FIG. 33 isconfigured to produce a junction box having four bend lines laid out ina square, such as the junction box described in U.S. Patent ApplicationNo. 60/665,577 filed Mar. 25, 2005 and entitled THREE-DIMENSIONALSTRUCTURE FORMED WITH PRECISION FOLD TECHNOLOGY AND METHOD OF FORMINGSAME, the entire contents of which application is incorporated herein bythis reference.

As noted above, bend controlling displacements may be formed in sheetmaterials in accordance with the present invention by a variety ofmeans. For example, prototypes, “one-offs” and other lower volumeproduction runs may be produced using laser cutting, water-jet cutting,oxyacetylene cutting, and other suitable means. Medium volume productionruns can be produced utilizing various soft-tooling methods including,but not limited to, CNC controlled tools, punches and dies such asturret punch press assemblies. High volume production runs may beproduced using various hard tooling methods including, but not limitedto, CNC-controlled presses and progressive dies, as well as non-CNCcontrolled presses and progressive dies. One will also appreciate thatany of the above methods of manufacture may be facilitated byappropriate software design and/or control applications, such as thosedescribed by U.S. Patent Application Publication No. US 2005/0005670 A1to Durney et al. entitled METHOD OF DESIGNING FOLD LINES IN SHEETMATERIAL, the entire contents of which application is incorporatedherein by this reference.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the Claims appended hereto and theirequivalents.

1. A method of preparing a sheet of material for bending along a bendline comprising the step of: providing one or more punch blades;inserting the punch blades into a punch blade block configured tocooperate with a die block; forming one or more displacements in thethickness direction of the sheet of material corresponding in number tothe number of punch blades, the displacement including a flat zonesubstantially parallel to the sheet of material with a portion of theperiphery of the flat zone extending along and adjacent to the bendline.
 2. The method of claim 1 wherein, the providing step isaccomplished by providing the punch blades in one or more standardizedsizes.
 3. The method of claim 2, wherein the width dimension of thepunch blades is approximately 2 mm, 3 mm or 4 mm.
 4. The method of claim2, wherein the width dimension of the punch blades is approximately 2mm, and the length dimension is approximately 4 mm, 8 mm, or 16 mm. 5.The method of claim 2, wherein the width dimension of the punch bladesis approximately 3 mm, and the length dimension is approximately 6 mm,12 mm, or 24 mm.
 6. The method of claim 2, wherein the width dimensionof the punch blades is approximately 4 mm, and the length dimension isapproximately 8 mm, 16 mm, or 32 mm.
 7. The method as defined in claim1, wherein, the forming step providing the portion of the peripheryadjacent the bend line with an edge and the sheet of material with acorresponding opposed face configured and positioned to produceedge-to-face engagement of the sheet of material during bending.
 8. Themethod as defined in claim 1, wherein, the forming step is accomplishedusing one of a stamping process, a punching process, a roll formingprocess, a shearing knife-based and an embossing process.
 9. The methodas defined in claim 1, wherein, the forming step is accomplished byarranging a plurality of punch blades along a plurality of bend lines,wherein a plurality of bend lines are formed simultaneously.
 10. Themethod as defined in claim 1, wherein, during the forming step,positioning the periphery portion of displacements on opposite side ofthe bend line at a jog distance from each other less than the thicknessdimension of the sheet of material.
 11. The method as defined in claim1, wherein, the bending straps have a strap width that is approximately6 times the thickness of the material.
 12. A tooling assembly forforming bend-controlling displacements in a sheet of material suitablefor bending along a bend line comprising: one or more punch blades; apunch blade block having one or more recesses dimensioned and configuredto removably receive said punch blades; a die block having one or morerecesses corresponding in number to the number of punch blade blockrecesses, one of said die block and said punch blade block beingconfigured to reciprocate with respect to the other; wherein said punchblades and said die block recesses are configured to form displacementshaving a flat zone substantially parallel to the sheet of material witha portion of the periphery of the displacement extending along andadjacent to the bend line.
 13. The tooling assembly of claim 12 wherein,the providing step is accomplished by providing the punch blades in oneor more standardized sizes.
 14. The tooling assembly of claim 12 whereinthe width dimension of the punch blades is approximately 2 mm, 3 mm or 4mm.
 15. The tooling assembly of claim 12 wherein the width dimension ofthe punch blades is approximately 2 mm, and the length dimension isapproximately 4 mm, 8 mm, or 16 mm.
 16. The tooling assembly of claim 12wherein the width dimension of the punch blades is approximately 3 mm,and the length dimension is approximately 6 mm, 12 mm, or 24 mm.
 17. Thetooling assembly of claim 12 wherein the width dimension of the punchblades is approximately 4 mm, and the length dimension is approximately8 mm, 16 mm, or 32 mm.
 18. The tooling assembly of claim 12 wherein, thepunch blade block is configured to position a portion of the peripheryadjacent the bend line with an edge and the sheet of material with acorresponding opposed face configured and positioned to produceedge-to-face engagement of the sheet of material during bending.
 19. Thetooling assembly of claim 12 wherein, a plurality of punch blades arearranged along a plurality of bend lines and configured to form aplurality of bend lines simultaneously.
 20. The tooling assembly ofclaim 12 wherein, a plurality of punch blades are arranged to orient theperiphery portion of displacements on opposite side of the bend line ata jog distance from each other less than the thickness dimension of thesheet of material.
 21. The tooling assembly of claim 12 wherein, thepunch blades are arranged to form bending straps having a strap widththat is approximately 6 times the thickness of the material.